Ruth Teschner Costantino (1892-1981) was a fine art and antique dealer in New York City.
She began working for a specialist and dealer in Old Master wood engravings and original drawings and several years later founded her first gallery, Teschner Gallery. In 1922, Costantino assisted Carl Robert Lamm, owner of the Swedish castle Nasby Slott, selling an extensive collection of paintings, tapestries, rugs, fabrics, armor, and more. Costantino's work with the Lamm Collection helped establish herself as a highly regarded authority on European antique art and furniture. In 1935, Costantino moved Teschner Gallery uptown and renamed it Connoisseur Inc. Throughout her career, Costantino advised the private collections of Madame Consuelo Vanderbilt Balsan, Mrs. Henry Ford II, Mr. Stavros Niarchos, Mrs. John D. Rockefeller II, and many more; served as the White House´s principal purveyor of French eighteenth-century furniture during the Kennedy administration; and dealt fine arts, furniture, and other antique items to U.S. museums, including the Metropolitan Museum of Art, National Gallery of Art, Museum of Fine Arts in Boston, and J. Paul Getty Museum in Los Angeles, and internationally to the Uffizi in Florence and the Brera Museum in Milan. After Costantino died in 1981, Connoisseur Inc. merged with L'Antiquaire gallery, founded by Constantino's daughter, Helen Costantino Fioratti, in 1965.
Costantino's husband, Arturo Costantino, was an Italian diplomat and banker who had a substantial role in the building of the Italian Pavilion at the 1939 World's Fair.